This article describes how to create a rechargeable push-to-start/hold-to-stop toy car ( Figure 1 ) using HVPAK 
SLG47105. The following design provides constant voltage on the motor regardless of battery charge and Push-to-Start/Hold-to-Stop capability. Thanks to the Hold-to-Stop functionality, the car automatically turns off when it gets stuck. So, if the child drives somewhere and forgets the toy, the car will turn off and no longer consume energy, saving battery. CC-CV battery charger control is also implemented.
Just an SLG47105 and a few extra components allow you to create a complete device with load control, motor drive, overcurrent protection and other interface features.
Figure 1: A prototype of a toy car
Operation principle
The complete circuit schematic is presented in Figure 2 .
Figure 2: Complete circuit diagram
Brushed DC motor is used for this project. If the car is pushed, the SLG47105 detects it and the car starts moving. If pressed and held, the system will turn off. The device is powered by a 3.7V lithium-ion battery. When the USB charger is connected, the SLG47105 detects the voltage level and the appropriate CC-CV charging stage begins. The motor is blocked during charging.
There are also three LEDs to notify about the process.
LED1 (RED) is CHARGED. Flashing represents the charging process. The LED lights up when charging is complete. The LED is off when no USB is connected.
LED2 (BLUE) is STATUS. If you BAT < 3 V – flashing. If you STICK > 3 V – the LED is on if the car is moving and the LED is off when the car is not moving.
LED3 (BLUE and RED) flashing means car movement.
The proposed PCB design is shown in Figure 3 .
Figure 3: HVPAK demo car PCB
GreenPAK Design consists of two parts: Car Engine Control and USB Charger. The design file can be downloaded here Rechargeable toy car with Push-to-Start/Hold-to-Stop functionality.hvp. It was created in Go Configure 
Software Hub Renésias.
The motor control part is shown in Figure 4 .
Figure 4: Car engine GreenPAK project
The PWM0 block provides a ~50 kHz signal with a PWM depending on the motor load voltage. The HV_GPO0_HD and HV_GPO1_HD of the Differential Amplifier with Integrator and Comparator are connected to the Diff+ and Diff- of the HV OUT CTRL0 (first Full Bridge). This macrocell is useful when there is a need to maintain constant voltage in the Full Bridge load. The integrated DC voltage level is applied to the negative input of the comparator. The comparator outputs are used to control the PWM duty cycle. In this case, a closed-loop system controls the PWM duty cycle to ensure constant average output voltage level.
The ACMP1H is connected to the engine's M terminal and checks whether the car has been pushed. When the shaft of the DC motor rotates in the coil according to the law of electromagnetic induction, an electromotive force (EMF) is induced. This signal is detected by ACMP1H. Its output goes to DFF13 which then enables the PWM0 block. 4-bit LUT1 provides an enable signal to LED3 when the car is ON. To prevent battery discharge, the ACMP1H is connected to the 50 ms Wake Sleep Controller.
When the DC motor shaft is kept stationary, the current increases. CCMP1 is connected to the Sense A resistor (PIN5) and monitors the current. Its output goes to MF1, which detects exceeding this current limit. If it lasts longer than 500 ms (CNT1/DLY1), the HIGH signal of the 4-bit LUT0 resets DFF13 and the system shuts down. HV OUT CTRL0 is turned off with a 300 ms delay to give the engine some time to stop and prevent system reset. Additionally, the VUSB detection signal is connected to 4-bit LUT0, so if it is HIGH (USB is connected), the system will also shut down.
MF3 and PGEN provide control and selection functions for LED1 and LED2 described in Section 1. The USB Charger part is shown in Figure 5 .
Figure 5: GreenPAK USB charger design
If Vusb is connected, PIN3 detects it and turns on ACMP0H. The ACMP0H checks the Vbat voltage. The output of DFF6 is HIGH, therefore no voltage divider is connected to PIN19 (Source IN+ with gain x8 of ACMP0H). If Vbat is less than 3 V, the Precharging phase begins. PWM1 sets the current and CCMP1 controls it. In this case, the Up/Down input of the PWM1 macrocell is LOW, which means we start charging from Vref = 160 mV for CCMP1 Vref (Figure 6). As a result, CCMP1 maintains 67 mA current:
Once the ACMP0H output is HIGH (Vbat is greater than 3.0V), the DFF6 output goes LOW and the voltage divider is connected to PIN19. The Constant Current phase begins. In this case, the ACMP0H makes a comparison for 4.2 V (and not 3.0 V as in the 1st case). PWM1 Up/Down input is HIGH, so CCMP1 Vref is 960 mV. The resulting current is ~400 mA. Note that these current limits can be changed by changing the Vref value in the Reg File or by changing the resistor connected to PIN 12 (Sense B).
This DC phase continues until the battery voltage reaches 4.2 V (ACMP0H output is HIGH). Then the Constant Current stops and the Constant Voltage phase begins. PWM1 Up/Down input is LOW, so CCMP1 Vref is 160 mV. In this case, the ACMP0H controls the constant voltage of 4.2 V, and the CCMP1 only checks and maintains the decreasing current and lower than the current of 67 mA until the battery is fully charged. When the battery is fully charged, the charging process stops and all corresponding blocks are in Sleep mode (CHG_Sleep is HIGH).
Figure 6: CCMP1 Vref reg file data
Device Test
Please also see the video of the working rechargeable toy car with Push-to-Start / Hold-to-Stop functionality.
The following Figures 7-12 show the signal at the motor terminal depending on the VDD (Vbat).
Figure 7: VDD = 3.0 V, duty cycle 43%
Figure 8: VDD = 3.4 V, 40% duty cycle
Figure 9: VDD = 3.4 V, 40% duty cycle
Figure 10: VDD = 3.7 V, duty cycle 35%
Figure 11: VDD = 4.2 V, duty cycle 31%
Figure 12: Spike at PIN20 (terminal M) during Push-to-Start
Conclusion
This article describes how to configure the HVPAK to create a rechargeable toy car with push-to-start/hold-to-stop functionality. The results prove that the circuit works as expected, and the SLG47105 is capable of acting as a control module for the brushed DC motor and the 3.7V lithium-ion battery charger at the same time.
GreenPAK's internal resources, including HV, oscillators, logic, and GPIOs, are easy to configure to implement the desired functionality for this project.
